Why Bicarb Could Be Your Secret Weapon for Summer Marathons
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It was a warm weekend across the UK, with both the London and Manchester Marathons taking place under unusually hot spring conditions. The heat caught many runners off guard, leading to widespread struggles with pacing, hydration, and cramping.
In challenging condistions, I (Josh) ran a personal best of 2hrs 23mins and 29seconds, and I credit Bicarrb with giving me a performance boost in the second half, which helped me move from ~85th to 46th overall. Read on to learn more about why.
The Electrolyte Angle
Most runners know that sodium bicarbonate is commonly used to buffer acid during high-intensity efforts, but far fewer consider its role as a sodium source. A typical dose of bicarb used for endurance performance (around 0.2–0.3g per kg of body mass) contains a significant amount of sodium—around 4g in a 16g bicarrb portion. That’s more than you'd get from a salt capsule, without needing to add an extra supplement.
This is particularly helpful in long, hot races. When you sweat, sodium is the primary electrolyte you lose. Failing to replace it can lead to cramping, reduced performance, or even hyponatremia if you're also over-consuming plain water. Taking Bicarrb before a race can front-load some of that sodium, supporting hydration and electrolyte balance right from the start.
A Personal Case Study: London Marathon
At this year's London Marathon, I ran a controlled race despite the hot conditions — I held close to even splits throughout with my first half just 1minute quicker. Ahead of the race, I took a standard dose of bicarrb—not just for the performance buffering effect, but also to boost my sodium intake. While it’s always hard to isolate one factor in race day success, I strongly believe this contributed to maintaining steady energy and avoiding the fade that so often comes in the second half of a marathon.
A Two-in-One Advantage
As we move into the summer months and the racing calendar fills with marathons and ultras, this two-in-one benefit becomes even more relevant. With bicarb, you’re not only supporting your body’s ability to buffer acidity, but also helping it manage heat stress and hydration through smarter sodium intake.